Introduction to Pulleys

A pulley is a simple machine that transfers power and changes the direction of a lift to make rigging easier. It contains a wheel that carries a rope on its rim.

A pulley, carabiner and lanyard

The physics behind pulleys is fairly straightforward. When you add more of them into a system you get a higher mechanical advantage. So, when a system contains only 1 pulley you can get either a 1:1 or a 2:1 mechanical advantage dependent on how you set it up.

NOTE: We’ll dive into building pulley systems in Part 2 of this series.

Types of Pulleys

Pulleys come in various shapes and sizes but fall into 3 system categories:

• Fixed

• Movable

• Compound

Fixed

A system where the pulley is attached to a fixed point and the lifting line is attached to your object.

A fixed pulley is fixed to the anchor

With fixed pulleys the amount of force applied on the pulling side is equal to the amount exerted on the lifting side.

A fixed pulley provides absolutely no efficiency (in fact you might lose some), but this type of pulley is great for changing your lift or pull direction and can be worked into a larger system.

Movable

A system where the pulley is attached to your object with one end of rope attached to a fixed point and the other end, the lifting line, is free.

A movable pulley moves with the object

Movable pulleys actually move with the load, hence their name. The force applied on the pulling side multiplies on the lifting side. This type of pulley system does provide efficiency.

Compound

Combining “Fixed” and “Movable” into one system.

The movable pulley multiplies the force and the fixed pulley changes the direction of your lift.

A compound pulley system combines both fixed and movable pulleys

The Pulleys That Grips Use

I most commonly use ⅜” multiline with ⅜” pulleys. Snatch block pulleys (see below) are my go-to, but I know a lot of other grips prefer to use swivel eyes (also see below).

Some will use a combination of snatch blocks, swivel eyes and locking. It all depends on your needs. That’s why we work with a wide variety - you’ll always have what you need.

Most of the pulleys we use require carabiners or shackles for attachment.

SAFETY NOTE: it’s important to use pulleys that are rated and clearly labeled in pounds. If you’re rigging or hanging anything over people’s heads or creating any structures that will support people use a 5:1 design factor for safety. For systems that don’t involve hanging any objects or rigging over people, you may use a 3:1 design factor.

⅜” multiline coiled up in 50’ hanks

Snatch Block Pulley

Snatch Blocks are the workhorse of grip work and are the pulleys you’ll most likely find on any grip truck. They swivel open to accept a rope and can be closed by throwing a carabiner or lanyard through the top hole.

We use snatch blocks for a few reasons:

• They’re relatively cheap - around $75 per unit excluding carabiners and lanyards

• They allow you to attach the pulley into the middle of the rope because they swivel open so you don’t have to feed the rope through a fixed opening

• These have a high breaking strength relative to our normal use cases

Snatch block pulleys and carabiners

Double pulley

The double block adds more mechanical advantage into your system. It comprises of two pulleys built into 1 side by side unit.

A double pulley

A double block paired with one or more pulleys creates a block and tackle system (like below). We’ll fix the double pulley up high and move the other double pulley block with the load.

Block and tackle rig

A block and tackle provides you with the best of both worlds, a great mechanical advantage and a compact system.

Swivel eye pulley

A swivel eye is similar to a snatch block except for the fact that your mounting point rotates. This is useful when you want to change the direction of your pull, where the angle of a fixed snatch block might not line up in your required pull direction.

I’m a huge fan of swivel eyes with the swing open side plates for easy line integration and the only reason I don’t have all swivel eyes on my grip truck is because they are expensive and take up a lot of space. Plus, if I rig my snatch blocks properly then I don’t normally need any swivel functionality.

Rock exotica swivel eye pulleys

Locking pulley

What makes locking pulleys fantastic is they are progress-capture meaning once engaged, your load will only travel in one direction. I use them all the time for softboxes and lighting rigs. Pulling up and tying off is easy with them because you don’t need someone to hold the line while waiting to tie off. It locks itself!

You activate and deactivate the progress capture mechanism manually. Deactivating the progress capture requires that you actually be at the pulley. So, when you are ready to come down with your load you need to go up to the pulley, deactivate progress capture and let out your line. For this reason, I try and rig my locking pulleys down low where I can access them. When the progress capture is deactivated the locking pulley will act as a normal pulley where the line can travel in either direction so you can lower your load back down to the ground.

Without a locking pulley the simplest form of progress capture is to add prusiks on the load side of the pulley. The locking pulley is better because sometimes these prusiks get sucked into the pulley causing all kinds of problems! If you are going to use a prusik, use a prusik minding pulley to help prevent this.

Petzl locking pulleys ready to be integrated into a rig

Rope size and efficiency

As grips we most commonly use 3/8” multiline. Multiline II is a 3-strand composite rope constructed by twisting three strands of a blend of spun and filament polyester around cores of fibrillated polyolefin.

Lifting up an 8x8 softbox skeleton with multiline

From Jack Rubin & Sons: ”The polyolefin keeps the strands firm and round without adding weight, which improves abrasion resistance and handling. The spun polyester gives Multiline II its characteristic fuzzy feel and makes it easier to grip, even when it’s wet.

Multiline II provides the greatest durability, highest strength, lightest weight, and most consistent supple feel over time of any commercially available composite rope.”

The tensile breaking strength of the Multiline II we use is 3,500 lbs. This rope starts out a little stiff but breaks in nicely with wear. It has great knot holding ability, which is perfect for gripping.

Ever tried to tie a knot with some chunky, synthetic line? It doesn’t seem like it wants to hold. One shake of the line and it’ll fall apart. You don’t get that with multiline.

When using pulleys it is important to match your rope and pulley sizes. You want a pulley that can handle the width of your rope. When your line thickness and pulley channel width don’t match, you’ll lose most of your efficiency and safety could be compromised.

When I need less stretch in a pulley system I will switch from 3/8 multiline to tech 12.

Technora 12 (the official name) features extremely high tensile strength, minimal stretch, low creep, and excellent heat resistance. It is typically coated with black urethane.

Tech 12 is high strength and low stretch

We don’t use tech 12 for all our applications because it is super expensive and this can be overkill for simple use. Stunts use tech 12 for a lot of systems they build.

Carabiners & Lanyards

I carry high tensile steel D-style auto-lock carabiners for most of my pulley rigging. They have a gate strength of 3,600 lbs and a minimum breaking strength of 9,217 lbs. I own 40 snatch block pulleys with 40 matching carabiners and lanyards and have only used them all at once on one job where we hung a lot of points for lights and blue screens.

I only use carabiners that have automatic locking gates. Specifically, twist lock.

Opening automatic locking pulleys may take a few hand motions - often referred to as double or triple action.

The twist lock is quick, effective and safe. When you’re ready to close the carabiner, just let go of the twist lock and it falls into place, securely locking the carabiner.

The keeper pin is a nice-to-have feature that we don’t use often

Can carabiners be used in place of pulleys?

In a pinch, yes, but using a carabiner instead of a pulley significantly decreases the efficiency of your pull. High quality pulleys have about 90% efficiency whereas carabiners will have 50% efficiency in a 1:1 pull.

Below are the round slings (also called “runners” and “lanyards”) that I use. These can can hold 4,850 lbs and pair perfectly with my pulleys and carabiners for most applications.

The round slings I use

Safety concerns

As is customary, let’s talk a bit about safety. A good grip is a safe grip. All pulleys are not created equal. Choosing the correct pulley is just as important as setting up a safe system.

Choosing the right pulleys

Avoid Home Depot pulleys for anything other than hanging your kayak in your garage! Even then I wouldn’t trust those things further than I can throw them. Most of those pulleys have either a 350 or 500 rating and even then aren’t put through the same vigorous safety tests that our rigging equipment is subject to.

Avoid Home Depot pulleys like the plague

When doing any overhead rigging, it’s important to purchase pulleys specifically designed for high capacity loads with clearly identified and certified weight ratings.

Remember, when flying things overhead, we use a 5:1 design ratio. If you work with anything less, you are putting people’s lives in jeopardy!

Avoid using any pulleys that aren’t clearly marked with a load rating that is 5x your lifting weight.

From here, it’s all about setting your pulleys up in a system that works for your needs which we’re covering in Part 2 of this series: Building Pulley Systems.

Conclusion: The Power of Pulleys in Grip Work

Pulleys might be simple machines, but they're incredibly powerful tools that solve complex rigging challenges on set. From enabling impromptu camera movements to safely suspending lighting rigs, they are are indispensable to any professional grip.

Here’s the key things to remember:

• The Three Fundamental Pulley Systems:

  • Fixed pulleys that change direction but provide no mechanical advantage

  • Movable pulleys that travel with the load and multiply force

  • Compound systems that combine both for maximum efficiency and directional control

• Specific Pulley Types:

  • Snatch blocks for easy rope integration

  • Double pulley blocks for increased mechanical advantage

  • Swivel eyes for directional flexibility

  • Locking pulleys for progress capture

• Safety is paramount when rigging overhead

  • Always use properly rated pulleys (clearly labeled with weight ratings).

  • Apply the 5:1 design factor for systems over people's heads.

  • Match your rope size to your pulley channel width for maximum efficiency.

Stay tuned for Part 2 of this series, where we'll dive into building complete pulley systems that put these principles into practice.